2-Deoxy-D (3H) glucose (3H 2-DG) uptake was studied in isolated normal cerebral capillaries subjected to various gas mixtures during incubation. Under 100% N2 atmosphere, the specific 3H 2-DG capillary uptake was markedly decreased but could be recovered by substituting the N2 gas for oxygen or normal air. Moreover the addition of free fatty acid serum albumin prevented the reduction of 3H 2-DG capillary uptake under anaerobic conditions.